U.S. patent number 7,403,458 [Application Number 10/766,328] was granted by the patent office on 2008-07-22 for compatible optical pickup and light output amount detecting method performed in the compatible optical pickup.
This patent grant is currently assigned to Samsung Electronics Co., Ltd.. Invention is credited to Chun-gi Kim, Eun-goo Kim, Ju-hyung Lee, Ji-hwan Lim, Kyoung-hwan Park, Pyong-yong Seong.
United States Patent |
7,403,458 |
Lim , et al. |
July 22, 2008 |
**Please see images for:
( Certificate of Correction ) ** |
Compatible optical pickup and light output amount detecting method
performed in the compatible optical pickup
Abstract
A compatible optical pickup, including first and second light
sources for emitting lights with different wavelengths and first
and second photodetectors for detecting an information signal
and/or an error signal, and a method of detecting the amount of
output light using the compatible optical pickup. The first and
second photodetectors monitor the amount of light output from the
second and first light sources respectively such that no extra
front photodetectors are required. Thus, the number of optical
component parts included in the optical pickup can be reduced,
thereby lowering the manufacturing costs for the optical pickup.
Also, there is no need to secure a space in a base where a front
photodetector is to be installed, so the base is simplified. Thus,
inferior moldings are reduced, and the durability of a mold can be
prolonged.
Inventors: |
Lim; Ji-hwan (Suwon-si,
KR), Lee; Ju-hyung (Suwon-si, KR), Seong;
Pyong-yong (Seoul, KR), Kim; Eun-goo (Suwon-si,
KR), Kim; Chun-gi (Suwon-si, KR), Park;
Kyoung-hwan (Suwon-si, KR) |
Assignee: |
Samsung Electronics Co., Ltd.
(Suwon-Si, KR)
|
Family
ID: |
32653310 |
Appl.
No.: |
10/766,328 |
Filed: |
January 29, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040257925 A1 |
Dec 23, 2004 |
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Foreign Application Priority Data
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Jan 29, 2003 [KR] |
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10-2003-0005925 |
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Current U.S.
Class: |
369/53.26;
369/112.1; G9B/7.1 |
Current CPC
Class: |
G11B
7/123 (20130101); G11B 7/1275 (20130101); G11B
7/1263 (20130101); G11B 2007/0006 (20130101) |
Current International
Class: |
G11B
7/00 (20060101) |
Field of
Search: |
;369/53.26-53.27,44.23,44.37,94,103 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 160 778 |
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Dec 2001 |
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EP |
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1 174 865 |
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Jan 2002 |
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EP |
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Other References
European Search Report dated Mar. 29, 2007. cited by other.
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Primary Examiner: Young; Wayne
Assistant Examiner: Bibbins; LaTanya
Attorney, Agent or Firm: Staas & Halsey LLP
Claims
What is claimed is:
1. An optical pickup, which is compatible with a first recording
medium having a first format and a second recording medium having a
second format different from the first format, the optical pickup
comprising: a first light source which emits a first light beam,
the first light beam having a wavelength suitable for the first
recording medium; a first photodetector which detects an
information signal associated with the first recording medium and
based upon the first light beam; a second light source which emits
a second light beam, the second light beam having a wavelength
suitable for the second recording medium; and a second
photodetector which detects an information signal associated with
the second recording medium and based upon the second light beam,
wherein the first photodetector monitors the amount of light
emitted from the second light source by detecting a part of the
second light beam that is emitted from the second light source and
is incident on the first photodetector through a reflection
process, and/or the second photodetector monitors the amount of
light emitted from the first light source by detecting a part of a
first light beam that is emitted from the first light source and is
incident upon the second photodetector through a reflection
process.
2. The optical pickup of claim 1, further comprising at least one
of: a first detection circuit which is coupled to the first
photodetector and produces a monitoring signal in proportion to the
amount of light emitted from the second light source; and a second
detection circuit which is coupled to the second photodetector and
produces a monitoring signal in proportion to the amount of light
output from the first light source.
3. The optical pickup of claim 1, wherein the first photodetector
monitors the amount of light emitted from the second light source
by detecting a second light beam that is emitted from the second
light source, reflected by a recording medium, and then incident
upon the first photodetector, and/or the second photodetector
monitors the amount of light output from the first light source by
detecting a first light beam that is emitted from the first light
source, reflected by the recording medium, and then incident upon
the second photodetector.
4. The optical pickup of claim 3, further comprising a plate-type
beam splitter transmitting and reflecting each of the first and
second light beams at a predetermined ratio.
5. The optical pickup of claim 1, further comprising a reflection
element which reflects a portion of each of the first and/or second
light beams and is installed on a path common to the first and
second light beam emitted from the first and second light source,
and the first photodetector monitors the amount of light emitted
from the second light source by detecting a second light beam that
is emitted from the second light source, reflected by the
reflection element, and then incident on the first photodetector,
and/or the second photodetector monitors the amount of light
emitted from the first light source by detecting a first light beam
that is emitted from the first light source, reflected by the
reflection element, and incident upon the second photodetector.
6. The optical pickup of claim 5, further comprising a cubic beam
splitter which transmits and reflects each of the first and second
light beams at a predetermined ratio.
7. The optical pickup of claim 5, wherein the reflection element is
formed on a surface of the cubic beam splitter.
8. The optical pickup of claim 1, wherein one of the first and
second light sources emits a light beam with a wavelength suitable
for recording to and/or reproducing from a CD-family recording
medium, and the other one of the first and second light sources
emits a light beam with a wavelength suitable for recording to
and/or reproducing from a DVD-family recording medium.
9. The optical pickup of claim 8, wherein the compatible optical
pickup records an information signal to at least a part of the
CD-family recording medium.
10. The optical pickup of claim 8, wherein the compatible optical
pickup records an information signal to at least a part of the
DVD-family recording medium.
11. The optical pickup of claim 1, wherein the first photodetector
detects an error signal associated with the first recording medium
and based upon the first light beam, and the second photodetector
detects an error signal associated with the second recording medium
and based upon the second light beam.
12. The optical pickup of claim 1, wherein the first light source
and the first photodetector are separately installed.
13. The optical pickup of claim 1, wherein the second light source
and the second photodetector are separately installed.
14. The optical pickup of claim 1, further comprising a reflection
element, wherein the reflection element which reflects a portion of
each of the first and/or second light beam is installed on a path
common to the first and second light beam emitted from the first
and second light source, and the first photodetector monitors the
amount of light emitted from the second light source by detecting a
second light beam that is emitted from the second light source and
is reflected by the reflection element to be incident on the first
photodetector, and/or the second photodetector monitors the amount
of light emitted from the first light source by detecting a first
light beam that is emitted from the first light source and
reflected by the reflection element to be incident upon the second
photodetector.
15. The optical pickup of claim 14, further comprising a cubic beam
splitter which transmits and reflects each of the first and second
light beams at a predetermined ratio.
16. The optical pickup of claim 14, wherein the reflection element
is installed on a surface of the cubic beam splitter.
17. The optical pickup of claim 14, wherein the reflection element
is a coating on a light emission surface of the cubic beam
splitter.
18. An optical pickup comprising: a first hologram optical module
comprising; a first light source which emits a first light beam
with a wavelength suitable for a first recording medium, a first
hologram which changes the path of the first light beam, and a
first photodetector which receives light reflected by a recording
medium; and a second hologram optical module comprising; a second
light source which emits a second light beam with a wavelength
suitable for a second recording medium, a second hologram which
changes the path of the second light beam, and a second
photodetector, which receives light reflected by a recording
medium; wherein the first photodetector monitors the amount of
light emitted from the second light source by detecting a portion
of a second light beam that is emitted from the second light source
and incident on the first hologram optical module through a
reflection process, and/or the second photodetector monitors the
amount of light emitted from the first light source by detecting a
portion of a first light beam that is emitted from the first light
source and incident upon the second hologram optical module through
a reflection process.
19. The optical pickup of claim 18, wherein the wavelength of the
first light beam is different than the wavelength of the second
light beam.
20. The optical pickup of claim 18, wherein the first recording
medium has a first format and the second recording medium has a
second format different from the second format.
21. The optical pickup of claim 18, wherein the first light beam is
in a red wavelength range.
22. The optical pickup of claim 18, wherein the wavelength of the
first light beam is between 645 nm and 685 nm.
23. The optical pickup of claim 18, wherein the second light beam
is in an infrared wavelength range.
24. The optical pickup of claim 18, wherein the wavelength of the
second light beam is between 770 nm and 810 nm.
25. The optical pickup of claim 18, wherein the first and second
light sources are semiconductor lasers.
26. The optical pickup of claim 18, wherein the optical pickup
compatibly adopts DVDs and the first light beam is in a blue
wavelength range and the second light beam is in a red wavelength
range.
27. The optical pickup of claim 18, wherein each of the first and
second holograms serves as a light path conversion device, and the
first hologram transmits the first light beam emitted from the
first light source without changing a path thereof and diffracts
incident first and second light beams in .+-. first order and
transmits the .+-. first order diffracted light of the first and
second light beams to the first photodetector.
28. The optical pickup of claim 18, wherein the second hologram
transmits the second light beam emitted from the second light
source without changing a path thereof and diffracts incident first
and second light beams in .+-. first order and transmits the .+-.
first order diffracted light of the first and second light beams to
the second photodetector.
29. The optical pickup of claim 18, further comprising at least one
of: a first detection circuit which is coupled to the first
photodetector and produces a monitoring signal in proportion to the
amount of light emitted from the second light source; and a second
detection circuit which is coupled to the second photodetector and
produces a monitoring signal in proportion to the amount of light
emitted from the first light source.
30. The optical pickup of claim 18, wherein at least one of the
first detection circuit and second detection circuit comprises an
output terminal which outputs monitoring signal.
31. The optical pickup of claim 30, wherein each of the at least
one output terminals outputs an information reproduction signal,
that is, a radio frequency (RF) signal.
32. The optical pickup of claim 30, wherein each of the first and
second detection circuits further comprises a controller.
33. The optical pickup of claim 32, wherein each of the controllers
is a variable resistor which controls the amplification rate of a
monitoring signal.
34. The optical pickup of claim 18, wherein each of the at least
one output terminals may be a separately added terminal which
outputs a monitoring signal with respect to a typical PDIC.
35. The optical pickup of claim 18, wherein the first photodetector
monitors the amount of light emitted from the second light source
by detecting a second light beam that is emitted from the second
light source, reflected by a recording medium, and then incident
upon the first photodetector, and/or the second photodetector
monitors the amount of light emitted from the first light source by
detecting a first light beam that is emitted from the first light
source, reflected by the recording medium, and then incident upon
the second photodetector.
36. The optical pickup of claim 35, further comprising a plate-type
beam splitter which transmits and reflects each of the first and
second light beams at a predetermined ratio.
37. The optical pickup of claim 18, further comprising a reflection
element, wherein the reflection element which reflects a portion of
each of the first and/or second light beam is installed on a path
common to the first and second light beam emitted from the first
and second light source, and the first photodetector monitors the
amount of light emitted from the second light source by detecting a
second light beam that is emitted from the second light source and
is reflected by the reflection element to be incident on the first
photodetector, and/or the second photodetector monitors the amount
of light emitted from the first light source by detecting a first
light beam that is emitted from the first light source and
reflected by the reflection element to be incident upon the second
photodetector.
38. The optical pickup of claim 18, wherein one of the first and
second light sources emits a light beam with a wavelength suitable
for at least one of recording and reproducing a CD-family recording
medium, and the other one of the first and second light sources
emits a light beam with a wavelength suitable for at least one of
recording and reproducing a DVD-family recording medium.
39. The optical pickup of claim 38, wherein the compatible optical
pickup can record an information signal to at least a part of the
CD-family recording medium.
40. The optical pickup of claim 38, wherein the compatible optical
pickup can record an information signal to at least a part of the
DVD-family recording medium.
41. A method of detecting the amount of light output from at least
one of a first and a second light source using an optical pickup
which is compatible with a first recording medium and a second
recording medium, the first and second recording media having
different formats, the optical pickup comprising: a first light
source emitting a first light beam with a wavelength suitable for
the first recording medium; a first photodetector which detects at
least one of an information signal and an error signal associated
with the first recording medium; a second light source emitting a
second light beam with a wavelength suitable for the second
recording medium; and a second photodetector detecting at least one
of an information signal and an error signal associated with the
second recording medium, the method comprising: detecting at least
one of a portion of a second light beam that is emitted from the
second light source and incident on the first photodetector through
a reflection process, using the first photodetector, and a part of
a first light beam that is emitted from the first light source and
incident upon the second photodetector through a reflection
process, using the second photodetector; and producing at least one
of a monitoring signal for monitoring the amount of light emitted
from the second light source using a signal corresponding to the
second light beam detected by the first photodetector, and a
monitoring signal for monitoring the amount of light output from
the first light source using a signal corresponding to the first
light beam detected by the second photodetector.
42. The method of claim 41, wherein one of the first and second
light sources emits a light beam with a wavelength suitable for
recording and/or reproducing a CD-family recording medium, and the
other one of the first and second light sources emits a light beam
with a wavelength suitable for recording and/or reproducing a
DVD-family recording medium.
43. The optical pickup of claim 41, wherein the first photodetector
detects an error signal associated with the first recording medium,
and the second photodetector detects an error signal associated
with the second recording medium.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Patent Application
No. 2003-5925, filed on Jan. 29, 2003, in the Korean Intellectual
Property Office, the disclosure of which is incorporated herein in
its entirety by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a compatible optical pickup and a
method of detecting the amount of light output by the compatible
optical pickup.
2. Description of the Related Art
Recently, optical pickups have become more complicated, thereby
requiring a large number of component parts to meet demands, such
as, compatible adoption of various types of optical disks, an
increase in multiple speeds, and the like.
However, recent optical pickups must also be compact and slim in
consideration of a space limit partially due to the proliferation
of portable terminals (e.g., notebook computers and the like). In
order to meet the size constraints, recent optical pickups must
reduce the number of component parts.
The minimization of the number and size of component parts included
in an optical pickup is important for minimizing the manufacturing
costs of the optical pickup, as well as simplifying the design of a
base.
A typical optical pickup includes a separate front photodetector to
monitor the amount of light output from a light source. Generally,
the front photodetector is installed behind a cubic or plate-type
beam splitter that the optical pickup uses as a light path
converting device.
Typical optical pickups with separate front photodetectors have the
following problems. First, since typical optical pickups include a
large number of component parts, the manufacturing costs of the
optical pickups are high. Second, since a base must have a space in
which the front photodetectors are installed, the structure of the
base is complex, causing a poor flow of liquid material for the
base occuring during injection molding of the base. Hence, inferior
molding frequently occurs, and the durability of the mold used in
injection molding of the base decreases.
SUMMARY OF THE INVENTION
The present invention provides a compatible optical pickup,
designed without extra front photodetectors, to monitor the amount
of light output from a light source, and a method of detecting the
amount of light being output using the compatible optical
pickup.
According to an aspect of the present invention, there is an
optical pickup compatible with first and second recording media
using different formats, the optical pickup comprising first and
second light sources and first and second photodetectors. The first
light source emits a first light beam with a wavelength suitable
for the first recording medium. The first photodetector detects an
information signal and/or an error signal associated with the first
recording medium. The second light source emits a second light beam
with a wavelength suitable for the second recording medium. The
second photodetector detects an information signal and/or an error
signal associated with the second recording medium. The first
photodetector monitors the amount of light output from the second
light source by detecting a part of a second light beam that is
emitted from the second light source and is incident on the first
photodetector through a reflection process, and/or the second
photodetector monitors the amount of light output from the first
light source by detecting a part of a first light beam that is
emitted from the first light source and is incident upon the second
photodetector through a reflection process.
According to one aspect of the present invention, there is also a
compatible optical pickup comprising first and second hologram
optical modules. The first hologram optical module comprises: a
first light source which emits a first light beam with a wavelength
suitable for a first recording medium; a first hologram for
changing the path of the first light beam; and a first
photodetector which receives light reflected by a recording medium.
The second hologram optical module comprises: a second light source
which emits a second light beam with a wavelength suitable for a
second recording medium with a format different from the format of
the first recording medium; a second hologram for changing the path
of the second light beam; and a second photodetector which receives
light reflected by a recording medium. The first photodetector
monitors the amount of light output from the second light source by
detecting a part of a second light beam that is emitted from the
second light source and incident on the first hologram optical
module through a reflection process, and/or the second
photodetector monitors the amount of light output from the first
light source by detecting a part of a first light beam that is
emitted from the first light source and incident upon the second
hologram optical module through a reflection process.
According to an aspect of the present invention, the compatible
optical pickup further comprises: a first detection circuit which
is coupled to the first photodetector and produces a monitoring
signal in proportion to the amount of light output from the second
light source; and/or a second detection circuit which is coupled to
the second photodetector and produces a monitoring signal in
proportion to the amount of light output from the first light
source.
According to another aspect of the present invention, the first
photodetector monitors the amount of light output from the second
light source by detecting a second light beam that is emitted from
the second light source, reflected by a recording medium, and then
incident upon the first photodetector, and/or the second
photodetector monitors the amount of light output from the first
light source by detecting a first light beam that is emitted from
the first light source, reflected by the recording medium, and then
incident upon the second photodetector.
In this case, the compatible optical pickup further comprises a
plate-type beam splitter transmitting and reflecting each of the
first and second light beams at a predetermined ratio.
According to an aspect of the present invention, a reflection
element for reflecting a part of each of the first and/or second
light beams is installed on a path common to the first and second
light beams emitted from the first and second light sources, and
the first photodetector monitors the amount of light output from
the second light source by detecting a second light beam that is
emitted from the second light source and is reflected by the
reflection element to be incident on the first photodetector,
and/or the second photodetector monitors the amount of light output
from the first light source by detecting a first light beam that is
emitted from the first light source and reflected by the reflection
element to be incident upon the second photodetector.
According to an aspect of the present invention, the compatible
optical pickup further comprises a cubic beam splitter which
transmits and reflects each of the first and second light beams at
a predetermined ratio. The reflection element is installed on a
surface of the cubic beam splitter.
According to an aspect of the present invention, one of the first
and second light sources emits a light beam with a wavelength
suitable for recording and/or reproducing a CD-family recording
medium, and the other emits a light beam with a wavelength suitable
for recording and/or reproducing a DVD-family recording medium.
According to an aspect of the present invention, there is provided
a method of detecting the amount of light output from a first
and/or a second light source using an optical pickup which is
compatible with first and second recording media with different
formats by comprising first and second light sources and first and
second photodetectors. The first light source emits a first light
beam with a wavelength suitable for the first recording medium. The
first photodetector detects an information signal and/or an error
signal associated with the first recording medium. The second light
source emits a second light beam with a wavelength suitable for the
second recording medium. The second photodetector detects an
information signal and/or an error signal associated with the
second recording medium.
According to an aspect of the present invention, a part of a second
light beam that is emitted from the second light source and
incident on the first photodetector through a reflection process is
detected using the first photodetector, and/or a part of a first
light beam that is emitted from the first light source and incident
upon the second photodetector through a reflection process is
detected using the second photodetector. Thereafter, a monitoring
signal which monitors the amount of light output from the second
light source is produced using a signal corresponding to the second
light beam detected by the first photodetector, and/or a monitoring
signal for monitoring the amount of light output from the first
light source is produced using a signal corresponding to the first
light beam detected by the second photodetector.
Additional aspects and/or advantages of the invention will be set
forth in part in the description which follows and, in part, will
be obvious from the description, or may be learned by practice of
the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
These and/or other aspects and advantages of the invention will
become apparent and more readily appreciated from the following
description of the embodiments taken in conjunction with the
accompanying drawings in which:
FIG. 1 is a perspective view for schematically showing a compatible
optical pickup according to an embodiment of the present
invention;
FIG. 2 is a schematic view of the hologram optical module of FIG.
1;
FIG. 3 is a perspective view for schematically showing a compatible
optical pickup according to another aspect of the present
invention;
FIG. 4 shows the main output terminals of the detection circuit of
FIGS. 1 and 3; and
FIG. 5 schematically shows the configuration of a compatible
optical recording and/or reproducing apparatus comprising a
compatible optical pickup according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference will now be made in detail to the embodiments of the
present invention, examples of which are illustrated in the
accompanying drawings, wherein like reference numerals refer to the
like elements throughout. The embodiments are described below to
explain the present invention by referring to the figures.
A compatible optical pickup according to the present invention
includes first and second light sources for emitting light with
different wavelengths and first and second photodetectors for
detecting an information signal and/or an error signal. The second
photodetector is used to monitor the amount of light emitted from
the first source, and the first photodetector is used to monitor
the amount of light emitted from the second source.
FIG. 1 is a perspective view for schematically showing a compatible
optical pickup according to a first embodiment of the present
invention. Referring to FIG. 1, the compatible optical pickup
according to the first embodiment of the present invention can
compatibly adopt two or more types of recording media with
different formats, such as a high-density recording medium and a
low-density recording medium. The optical pickup of FIG. 1
comprises: first and second hologram optical modules 20 and 30, an
objective lens 29, a plate-type beam splitter 25, and first and
second collimating lenses 24 and 34, arranged in an optical
configuration. The objective lens 29 focuses incident light so as
to form a light spot that lands on a recording surface of a
recording medium 10. The plate-type beam splitter 25 transmits and
reflects incident light at a predetermined ratio. The first
collimating lense 24 is installed between the first hologram
optical module and the plate-type beam splitter 25, and the second
collimating lens 34 is installed between the second hologram
optical module and the plate-type beam splitter 25.
Reference numerals 27 and 37 denote reflective mirrors. The optical
configuration of the compatible optical pickup of FIG. 1 is
suitable for a structure which reduces the thickness of an optical
pickup to about a half of the thickness of an optical pickup with
no reflective mirrors, otherwise known as a slim type optical
pickup. An optical pickup according to the present invention may or
may not have the reflective mirrors 27 and 37.
Each of the first and second hologram optical modules 20 and 30 can
have a structure as shown in FIG. 2.
Referring to FIG. 2, the first hologram optical module 20
comprises: a first light source 21; a first hologram 23; and a
first photodetector 22. The first light source 21 emits light with
a predetermined wavelength that is suitable for recording on and/or
reproducing from a high-density recording medium.
The second hologram optical module 30 comprises: a second light
source 31, a second hologram 33, and a second photodetector 32. The
second light source 31 emits light with a predetermined wavelength
that is suitable for recording on and/or reproducing from a
low-density recording medium. The second light source 31 emits
light with a wavelength different from the light emitted from the
first light source 21.
According to an aspect of the embodiment of the present invention
as shown in FIG. 1, when the optical pickup compatibly adopts CDs
and DVDs, the first light source 21 emits a first light beam 21a in
a red wavelength range (e.g., a wavelength range of about 645 nm to
685 nm, preferably 650 nm), and the second light source 31
preferably emits a second light beam 31a in an infrared wavelength
range (e.g., a wavelength range of about 770 nm to 810 nm,
preferably 780 nm). Semiconductor lasers can be used as the first
and second light sources 21 and 31.
According to an aspect of the present invention, when the optical
pickup as shown in FIG. 1 compatibly adopts DVDs and
next-generation DVDs, the first light source 21 preferably emits
the first light beam 21a in a blue wavelength range (e.g., a
wavelength range of about 400 nm to 420 nm), and the second light
source 31 preferably emits the second light beam 31a in a red
wavelength range (e.g., a wavelength range of about 645 nm to 685
nm).
Each of the first and second holograms 23 and 33 serves as a light
path conversion device. The first hologram 23 transmits the first
light beam 21a emitted from the first light source 21 without
changing its path and diffracts incident first and second light
beams 21a and 31a in .+-. first order and transmits the .+-. first
order diffracted light to the first photodetector 22.
Similarly, the second hologram 33 transmits the second light beam
31a emitted from the second light source 31 without changing its
path and diffracts incident first and second light beams 21a and
31a in .+-. first order and transmits the .+-. first order
diffracted light to the second photodetector 32.
As described above, the first photodetector 22 receives the first
and second light beams 21a and 31a incident on the first hologram
optical module 20. More specifically, the first photodetector 22
receives a first light beam 21a that is reflected by the recording
medium 10 and mostly transmitted by the plate-type beam splitter
25, and detects an information signal and/or an error signal
associated with a high-density optical disk from the received first
light beam 21a. The first photodetector 22 also receives a second
light beam 31a that is reflected by the recording medium 10 and
partially transmitted by the plate-type beam splitter 25, and
detects a first monitoring signal from the received second light
beam 31a for monitoring the amount of light emitted from the second
light source 31.
According to another aspect of the present invention to be descried
later, the second light beam 31a that is received by the first
photodetector 22 and used to monitor the amount of light emitted
from the second light source 31 is reflected by a reflective
element 85 of FIG. 3 instead of the plate-type beam splitter
25.
As described above, the second photodetector 32 receives the first
and second light beams 21a and 31a incident upon the second
hologram optical module 30. More specifically, the second
photodetector 32 receives a second light beam 31 a that is
reflected by the recording medium 10 and mostly reflected by the
plate-type beam splitter 25, and detects an information signal
and/or an error signal associated with a low-density optical disk
from the received second light beam 31a. The second photodetector
32 also receives a first light beam 21a that is reflected by the
recording medium 10 and partially reflected by the plate-type beam
splitter 25, and detects a second monitoring signal from the
received first light beam 21a for monitoring the amount of light
emitted from the first light source 21.
According to the present invention as shown in FIG. 3 and to be
descried later, the first light beam 21 a that is received by the
second photodetector 32 and used to monitor the amount of light
emitted from the first light source 31 has been reflected by the
reflective element 85 of FIG. 3 instead of the plate-type beam
splitter 25.
The compatible optical pickup according to the embodiment of the
present invention as shown in FIG. 1 may include cubic beam
splitters and/or plate-type beam splitters instead of the first and
second holograms 23 and 33. Hence, the first light source 21 and
the first photodetector 22 may be separately installed, and
likewise for the second light source 31 and the second
photodetector 32.
According to an aspect of the present invention, the plate-type
beam splitter 25 transmits and reflects each of the first and
second light beams 21a and 31a at a predetermined ratio.
For example, the plate-type beam splitter 25 transmits most of the
first light beam 21a and reflects the rest of it. In this case, the
majority of the first light beam 21a emitted from the first light
source 21 passes through the plate-type beam splitter 25 and
travels toward the recording medium 10. Most of the first light
beam 21a reflected by the recording medium 10 is transmitted by the
plate-type beam splitter 25 toward the first hologram optical
module 20, and the rest is reflected by the plate-type beam
splitter 25 toward the second hologram optical module 30.
Hence, the second photodetector 32 of the second hologram optical
module 30 can receive a part of the first light beam 21a emitted
from the first light source 21 and accordingly monitor the amount
of light output from the first light source 21.
Also, the plate-type beam splitter 25 reflects most of the second
light beam 31a and transmits the rest of it. In this case, the
majority of the second light beam 31a emitted from the second light
source 31 is reflected by the plate-type beam splitter 25 toward
the recording medium 10. Most of the second light beam 31a
reflected by the recording medium 10 is re-reflected by the
plate-type beam splitter 25 toward the second hologram optical
module 30, and the rest is transmitted by the plate-type beam
splitter 25 toward the first hologram optical module 20. Hence, the
first photodetector 22 of the first hologram optical module 20 can
receive a part of the second light beam 31a emitted from the second
light source 31 and accordingly monitor the amount of light output
from the second light source 31.
The compatible optical pickup, according to the embodiment of the
present invention as shown in FIG. 1, utilizes a plate-type beam
splitter 25 and monitors the amount of light emitted from the first
light source 21 and/or the second light source 31 by using a signal
corresponding to the first light beam 21a reflected by the
recording medium 10 that the second photodetector 32 of the second
hologram optical module 30 detects and by using a signal
corresponding to the second light beam 31a reflected by the
recording medium 10 that the first photodetector 22 of the first
hologram optical module 20 detects.
Referring to FIGS. 2 and 3, to monitor the amount of light emitted
from the first light source 21 and/or the second light source 31, a
compatible optical pickup according to an aspect of the present
invention includes the reflection element 85 on the common path of
the first and second light beams 21a and 31a for reflecting a part
of the first light beam 21a and/or the second light beam 31a,
instead of using the first light beam 21a and/or the second light
beam 31a reflected by the recording medium 10.
Also, as shown in FIG. 3, the compatible optical pickup according
to an aspect of the present invention includes a cubic beam
splitter 80 for transmitting and reflecting each of the first and
second light beams 21a and 31a at a predetermined ratio, instead of
the plate-type beam splitter 25 of FIG. 1. The reflection element
85 can be installed on a light emission surface of the cubic beam
splitter 80. The reflection element 85 may be a coating on the
light emission surface of the cubic beam splitter 80 or a separate
element attached to the light emission surface thereof.
In the compatible optical pickup according to an aspect of the
present invention, the plate-type beam splitter 25 may be used
instead of the cubic beam splitter 80 as shown in FIG. 3. Also, in
the compatible optical pickup according to the present invention as
shown in FIG. 1, the cubic beam splitter 80 may be used instead of
the plate-type beam splitter 25.
The reference numerals of FIG. 3 that coincide with those of FIG. 1
denote like optical elements, thus, they will not be described
here.
As shown in FIG. 3, when the reflection element 85 is installed on
the common path of the first and second light beams 21a and 31a, a
part of the first light beam 21a, which is emitted from the first
light source 21 and transmitted by the cubic (plate-type) beam
splitter 80 (25), is reflected by the reflection element 85 toward
the second hologram optical module 30 and then incident upon the
second photodetector 32. Also, a part of the second light beam 31a,
which is emitted from the second light source 31 and reflected by
the cubic (plate-type) beam splitter 80 (25), is reflected by the
reflection element 85 toward the first hologram optical module 20
and then incident upon the first photodetector 22. Hence, the first
photodetector 22 can monitor the amount of light emitted from the
second light source 31, and/or the second photodetector 32 can
monitor the amount of light emitted from the first light source
21.
As shown in FIGS. 1, 2, and 3, the compatible optical pickups may
include a first detection circuit 40 and/or a second detection
circuit 50. The first detection circuit 40 is connected to the
first photodetector 22 and can produce the first monitoring signal
for monitoring the amount of light emitted from the second light
source 31. The second detection circuit 50 is connected to the
second photodetector 32 and can produce the second monitoring
signal for monitoring the amount of light emitted from the first
light source 21. Here, FIGS. 1 and 3 show examples in which the
first and second detection circuits 40 and 50 are included. The
first and second detection circuits 40 and 50 are photo detector
integrated circuits (PDICs) connected to the first and second
photodetectors 22 and 32, respectively.
According to an aspect of the present invention, the first
detection circuit 40 also detects an information signal and/or an
error signal associated with a high-density optical disk from a
signal corresponding to the first light beam 21a detected by the
first photodetector 22.
According to an aspect of the present invention, the second
detection circuit 50 detects an information signal and/or an error
signal associated with a low-density optical disk from a signal
corresponding to the second light beam 31a detected by the second
photodetector 32.
As shown in FIG. 4, each of the first and second detection circuits
40 and 50 comprises an output terminal 60 for outputting the first
and second monitoring signals. The output terminal 60 may serve as
an output terminal for outputting an information reproduction
signal, that is, a radio frequency (RF) signal. Alternatively, the
output terminal 60 may be a separately added terminal which outputs
a monitoring signal with respect to a typical PDIC.
The reason why a monitoring signal and an information reproduction
signal are output via an identical output terminal will now be
described. According to an aspect of the present invention, during
recording and/or reproduction of a high-density optical disk, the
first light source 21 of the first hologram optical module 20 emits
the first light beam 21a, and the first photodetector 22 of the
first hologram optical module 20 detects an information signal
and/or an error signal associated with the high-density optical
disk. The second light source 31 and the second photodetector 32 of
the second hologram optical module 30 are not used for recording
and/or reproduction of a high-density optical disk. At this time, a
part of the first light beam 21a reflected by the high-density
optical disk can be detected by the second photodetector 32, and
the second monitoring signal produced from the signal corresponding
to the detected first light beam 21a can be output via an output
terminal of the second detection circuit 50 that is common to a
monitoring signal and an information reproduction signal. Likewise,
during recording and/or reproduction of a low-density optical disk,
the first monitoring signal for monitoring the amount of light
emitted from the second light source 31 can be output via an output
terminal of the first detection circuit 40 that is common to a
monitoring signal and an information reproduction signal.
FIG. 4 shows an example in which each of the first and second
detection circuits 40 and 50 includes a controller 70, for example,
a variable resistor, for controlling the amplification rate of a
monitoring signal. In other words, when the controller 70 is
included, there is an advantage in that the amplification rate of
the first or second monitoring signal can be controlled.
Since the first and second detection circuits 40 and 50 can be
designed to have various structures by those skilled in the art
with reference to the above description of the invention, the
design of the first and second detection circuits 40 and 50 will
not be described and/or shown in greater detail.
In the above-described compatible optical pickups according to the
present invention, during recording and/or reproduction of a
high-density optical disk, the amount of light emitted from the
first light source 21 is monitored by the second photodetector 32
for use in detecting an information signal and/or an error signal
associated with a low-density optical disk. During recording and/or
reproduction of a low-density optical disk, the amount of light
emitted from the second light source 31 is monitored by the first
photodetector 22 for use in detecting an information signal and/or
an error signal associated with a high-density optical disk.
Accordingly, the compatible optical pickups according to the
present invention require no extra monitoring photodetectors, can
reduce the number of component parts compared with a conventional
front photodetector, and do not need to have a space for the
conventional front photodetector to be installed.
An example of the paths of the first and second light beams 21a and
31a emitted from the first and second hologram optical modules 20
and 30 will now be described using FIGS. 1 and 2. For the purpose
of the example, it will be assumed that the first hologram optical
module 20 is suitable for recording and/or reproducing high-density
optical disks, for example, DVDs, and the second hologram optical
module 30 is suitable for recording and/or reproducing low-density
optical disks, for example, CDs. The reflective mirrors 27 and 37
are assumed to fully reflect any light incident upon them, and thus
shall be ignored for the purposes of the example. In alternate
aspects of the present invention, various arrangements of multiple
or singular mirrors can be utilized without changing the operation
of the optical pickups.
When a DVD is used as the recording medium 10, the first optical
source 21 operates to emit the first light beam 21a, which is a
divergent light beam. The first light beam 21a is transmitted by
the first hologram 23 and collimated by the first collimating lens
24 so as to be a parallel beam. Then, the first light beam 21a is
incident upon the plate-type beam splitter 25, the first light beam
21a is then transmitted thereby toward the objective lens 29. The
first light beam 21a is incident upon the objective lens 29 and
condensed thereby so that a light spot lands on a recording surface
of the recording medium 10.
The first light beam 21a is reflected by the recording surface of
the recording medium 10 and is then incident upon the plate-type
beam splitter 25 via the objective lens 29. Most of the incident
first light beam 21a is transmitted by the plate-type beam splitter
25 toward the first hologram optical module 20, and the rest is
reflected by the plate-type beam splitter 25 toward the second
hologram optical module 30. The majority and minority of the first
light beam 21a are incident upon the first and second hologram
optical modules 20 and 30, respectively, diffracted and transmitted
by the first and second holograms 23 and 33, respectively, and then
incident upon the first and second photodetectors 22 and 32,
respectively. The first detection circuit 40 produces an
information signal and/or an error signal from a signal
corresponding to the majority of the first light beam 21a detected
by the first photodetector 22. The second detection circuit 50
produces the second monitoring signal for monitoring the amount of
light emitted from the first light source 21, from a signal
corresponding to the minority of the first light beam 21a detected
by the second photodetector 32. Hence, when the amount of light
emitted from the first light source 21 is controlled using a signal
corresponding to light detected by the second photodetector 32, it
can be controlled so that light emitted from the first light source
21 has an appropriate recording power for a DVD.
When a CD is adopted as the recording medium 10, the second optical
source 31 operates to emit the second light beam 31a, which is a
divergent light beam. The second light beam 31a is straightly
transmitted by the second hologram 33 and collimated by the second
collimating lens 34 so as to be a parallel beam. Then, the second
light beam 31a is incident upon the plate-type beam splitter 25 and
mostly reflected thereby toward the objective lens 29. The second
light beam 31a is incident upon the objective lens 29 and condensed
thereby so that a light spot lands on the recording surface of the
recording medium 10. The second light beam 31a is reflected by the
recording surface of the recording medium 10 and is then incident
upon the plate-type beam splitter 25 via the objective lens 29.
Most of the incident second light beam 31a is reflected by the
plate-type beam splitter 25 toward the second hologram optical
module 30, and the rest is transmitted by the plate-type beam
splitter 25 toward the first hologram optical module 20. The
majority and minority of the second light beam 31a are incident
upon the second and first hologram optical modules 30 and 20,
respectively, diffracted and transmitted by the second and first
holograms 33 and 23, respectively, and then made incident upon the
second and first photodetectors 32 and 22, respectively. The second
detection circuit 50 produces an information signal and/or an error
signal from a signal corresponding to the majority of the second
light beam 31a detected by the second photodetector 32. The first
detection circuit 40 produces the first monitoring signal for
monitoring the amount of light emitted from the second light source
31, from a signal corresponding to the minority of the second light
beam 31a detected by the first photodetector 22. Hence, when the
amount of light emitted from the second light source 31 is
controlled using a signal corresponding to light detected by the
first photodetector 22, it can be controlled so that light emitted
from the second light source 31 has an appropriate recording power
for a CD.
Since the paths of the light in the compatible optical pickup
according to an aspect of the present invention of FIG. 3 can be
sufficiently construed from the description above, it will not be
described here.
Each of the compatible optical pickups according to the present
invention may have an optical system in which the first light beam
21a emitted from the first light source 21 is reflected by the
plate-type or cubic beam splitter 25 or 80 toward the objective
lens 29 and in which the second light beam 31a emitted from the
second light source 31 is transmitted by the plate-type or cubic
beam splitter 25 or 80 toward the objective lens 29.
The above-described compatible optical pickups according to the
present invention and the above-described light output amount
detecting methods performed therein are only examples, and are not
intended to limit the present invention. Various changes in form
and details can be made in the present invention.
For example, a compatible optical pickup according to the present
invention may be designed so as to monitor the amount of light
output from a light source so that the output light is suitable for
only a high-density optical disk or a low-density optical disk. Of
course, this optical pickup structure can be sufficiently construed
from the embodiments of the present invention, thus, it will not be
described in greater detail.
Such compatible optical pickups according to the present invention
as described above can be used to record an information signal to
at least a part of a CD-series recording medium and/or to at least
a part of a DVD-series recording medium.
FIG. 5 schematically shows a configuration of a compatible optical
recording and/or reproducing apparatus comprising a compatible
optical pickup 100 according to the present invention. Referring to
FIG. 5, the compatible optical recording and/or reproducing
apparatus comprises: a spindle motor 105, the compatible optical
pickup 100, a driver 107, and a controller 109. The spindle motor
105 rotates a recording medium 10, which is an optical information
storage medium. The compatible optical pickup 100 is installed so
as to move over the recording medium 10 in the radial direction of
the recording medium 10 and reproduces data from and/or records
data to the recording medium 10. The driver 107 drives the spindle
motor 105 and the optical pickup 100. The controller 109 controls a
focusing servo, a tracking servo, and/or a tilting servo of the
compatible optical pickup 100. Reference numeral 102 denotes a
turntable, and reference numeral 103 denotes a clamp for chucking
the recording medium 10.
The compatible optical pickup 100 includes an optical system
designed to compatibly deal with a plurality of types of recording
media with different formats, for example, DVDs and CDs, and an
actuator (not shown) for driving the objective lens 29. DVDs and
CDs are mentioned only as examples, and are not intended to limit
the scope of the invention. The invention is intended to be used
with any form of optical media.
Light reflected by the recording medium 10 is detected by a
photodetector included in the compatible optical pickup 100, for
example, by the first or second photodetector 22 or 32 of the first
or second hologram optical module 20 or 30 of the compatible
optical pickup according to the present invention, in consideration
of the type of an adopted recording medium. The detected light is
converted into an electrical signal, and the electrical signal is
applied to the controller 109 via the driver 107. The driver 107
controls the rotation speed of the spindle motor 105, amplifies the
received electrical signal, and drives the compatible optical
pickup 100. The controller 109 controls a focusing servo command, a
tracking servo command, and/or a tilting servo command on the basis
of the electrical signal received from the driver 107 and sends the
controlled commands to the driver 107 so that the compatible
optical pickup 100 can perform focusing, tracking, and/or
tilting.
As described above, the compatible optical recording and/or
reproducing apparatus adopting the compatible optical pickup 100
according to the present invention can compatibly deal with a
plurality of types of recording media with different formats.
In a compatible optical pickup according to the present invention
as described above, a photodetector for use in detecting an
information signal and/or an error signal is used to detect a
signal for use in monitoring the amount of light output from a
light source, so that the amount of light output from the light
source can be monitored without extra front photodetectors. Thus,
the number of optical component parts that constitute an optical
pickup can be reduced, thereby lowering the manufacturing costs for
the optical pickup.
Also, there is no need to secure a space in a base where a front
photodetector is to be installed, so the base is simplified. Thus,
inferior moldings are reduced, and the durability of a mold can be
prolonged.
Although a few embodiments of the present invention have been shown
and described, it would be appreciated by those skilled in the art
that changes may be made in this embodiment without departing from
the principles and spirit of the invention, the scope of which is
defined in the claims and their equivalents.
* * * * *